1. Field of the Invention
The present invention relates to a method for preparing organic light-emitting diodes and, more particularly, to method for preparing organic light-emitting diodes in large sizes.
2. Description of Related Art
Organic light-emitting diodes (OLEDs) are advantageous in having low weight, thinness (less than 1 mm), high brightness, wide viewing angle (about 170°), no need for backlight, low energy consumption, short response time, high resolution, low heat emission, shock resistance, low producing cost, good flexibility etc, and therefore have drawn much attention to the research in the related fields.
FIG. 1 shows a conventional organic light-emitting diode, which includes: a substrate 11, an anode 12, a hole injection layer 13, a hole transporting layer 14, a light-emitting region 15, an electron transporting layer 16, an electron injection layer 17 and a cathode 18, in which the light-emitting region 15 is disposed between the hole transporting layer 14 and the electron transporting layer 16, and includes a single light-emitting layer or multiple light-emitting layers.
Organic light-emitting diodes can be classified into small molecular organic light-emitting diodes and polymer organic light-emitting diodes according to the types of organic light-emitting materials, in which small molecular organic light-emitting diodes are usually prepared by evaporation and polymer organic light-emitting diodes are mainly prepared by spin coating.
Although the small molecular organic light-emitting diodes in a multi-layered structure can be prepared by evaporation, evaporation is disadvantageous to large-scale manufacture of organic light-emitting diodes and control of content ratio of components included in each light-emitting layer. On the other hand, although the polymer organic light-emitting diodes can be prepared by simpler spin coating, undesirable miscibility between layers is serious during preparing a multi-layered structure. Accordingly, no simple method for stably preparing organic light-emitting diodes in a multi-layered structure has been developed. In particular, the method for preparing small molecular organic light-emitting diodes is limited to evaporation and thus small molecular organic light-emitting diodes cannot be prepared in large sizes.